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Date: Thu, 14 Dec 2023 00:09:56 -0700
From: jim.cromie@...il.com
To: Łukasz Bartosik <lb@...ihalf.com>
Cc: Jason Baron <jbaron@...mai.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Douglas Anderson <dianders@...omium.org>,
Guenter Roeck <groeck@...gle.com>,
Yaniv Tzoreff <yanivt@...gle.com>,
Benson Leung <bleung@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Vincent Whitchurch <vincent.whitchurch@...s.com>,
Pekka Paalanen <ppaalanen@...il.com>,
Sean Paul <seanpaul@...omium.org>,
Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
upstream@...ihalf.com
Subject: Re: [PATCH v2 09/15] dyndbg: add trace destination field to _ddebug
On Thu, Nov 30, 2023 at 4:41 PM Łukasz Bartosik <lb@...ihalf.com> wrote:
>
> Add trace destination field (trace_dst) to the _ddebug structure.
> The trace destination field is used to determine output of debug
> logs when +T is set. Setting trace_dst value to TRACE_DST_BITS(63)
> enables output to prdbg and devdbg trace events. Setting trace_dst
> value to a value in range of [0..62] enables output to trace instance.
>
FWIW, I think setting trace_dest = 0 maps naturally to global / event buf.
The reason class_id DFLT is 63 is that DRM_UT_CORE is 0,
and DFLT allowed it to remain unchanged.
> Signed-off-by: Łukasz Bartosik <lb@...ihalf.com>
> ---
> include/linux/dynamic_debug.h | 14 ++++++++++++--
> lib/dynamic_debug.c | 28 +++++++++++++++++++---------
> 2 files changed, 31 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index 684766289bfc..56f152e75604 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -60,9 +60,19 @@ struct _ddebug {
> #else
> #define _DPRINTK_FLAGS_DEFAULT 0
> #endif
> - struct {
> + struct dd_ctrl {
> unsigned int flags:8;
> - unsigned unused:24;
> + /*
> + * The trace destination field is used to determine output of debug
> + * logs when +T is set. Setting trace_dst value to TRACE_DST_MAX(63)
> + * enables output to prdbg and devdbg trace events. Setting trace_dst
> + * value to a value in range of [0..62] enables output to trace
> + * instance.
> + */
> +#define TRACE_DST_BITS 6
> + unsigned int trace_dst:TRACE_DST_BITS;
> +#define TRACE_DST_MAX ((1 << TRACE_DST_BITS) - 1)
> + unsigned unused:18;
> } ctrl;
> } __attribute__((aligned(8)));
>
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index f47cb76e0e3d..0dc9ec76b867 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -80,14 +80,24 @@ module_param(verbose, int, 0644);
> MODULE_PARM_DESC(verbose, " dynamic_debug/control processing "
> "( 0 = off (default), 1 = module add/rm, 2 = >control summary, 3 = parsing, 4 = per-site changes)");
>
> +static inline struct dd_ctrl *get_ctrl(struct _ddebug *desc)
> +{
> + return &desc->ctrl;
> +}
> +
> +static inline void set_ctrl(struct _ddebug *desc, struct dd_ctrl *ctrl)
> +{
> + desc->ctrl = *ctrl;
> +}
> +
> static inline unsigned int get_flags(const struct _ddebug *desc)
> {
> return desc->ctrl.flags;
> }
>
> -static inline void set_flags(struct _ddebug *desc, unsigned int val)
> +static inline unsigned int get_trace_dst(const struct _ddebug *desc)
> {
> - desc->ctrl.flags = val;
> + return desc->ctrl.trace_dst;
> }
>
> /* Return the path relative to source root */
> @@ -190,8 +200,8 @@ static int ddebug_change(const struct ddebug_query *query,
> {
> int i;
> struct ddebug_table *dt;
> - unsigned int newflags;
> unsigned int nfound = 0;
> + struct dd_ctrl nctrl = {0};
> struct flagsbuf fbuf, nbuf;
> struct ddebug_class_map *map = NULL;
> int __outvar valid_class;
> @@ -257,14 +267,14 @@ static int ddebug_change(const struct ddebug_query *query,
>
> nfound++;
>
> - newflags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
> - if (newflags == get_flags(dp))
> + nctrl.flags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
> + if (!memcmp(&nctrl, get_ctrl(dp), sizeof(struct dd_ctrl)))
> continue;
> #ifdef CONFIG_JUMP_LABEL
> if (get_flags(dp) & _DPRINTK_FLAGS_ENABLED) {
> - if (!(newflags & _DPRINTK_FLAGS_ENABLED))
> + if (!(nctrl.flags & _DPRINTK_FLAGS_ENABLED))
> static_branch_disable(&dp->key.dd_key_true);
> - } else if (newflags & _DPRINTK_FLAGS_ENABLED) {
> + } else if (nctrl.flags & _DPRINTK_FLAGS_ENABLED) {
> static_branch_enable(&dp->key.dd_key_true);
> }
> #endif
> @@ -272,8 +282,8 @@ static int ddebug_change(const struct ddebug_query *query,
> trim_prefix(dp->filename), dp->lineno,
> dt->mod_name, dp->function,
> ddebug_describe_flags(get_flags(dp), &fbuf),
> - ddebug_describe_flags(newflags, &nbuf));
> - set_flags(dp, newflags);
> + ddebug_describe_flags(nctrl.flags, &nbuf));
> + set_ctrl(dp, &nctrl);
> }
> }
> mutex_unlock(&ddebug_lock);
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>
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